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No time to lose on climate change: WMO

According to the World Meteorological Organisation (WMO), the global average surface temperature in 2015 is likely to be the warmest on record and to reach the symbolic and significant milestone of 1Â°C above the pre-industrial era.

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No time to lose on climate change: WMO

According to the World Meteorological Organisation (WMO), the global average surface temperature in 2015 is likely to be the warmest on record and to reach the symbolic and significant milestone of 1Â°C above the pre-industrial era.

But the research group behind the latest paper - published on Tuesday in the journal Geophysical Research Letters - sought to look back as far as possible to detect the earliest event that human activity - such as burning fossil fuels and clearing forests - could be said to have increased the chances of it occurring.

The first record breaking hot year scientists say was influence by climate change occurred in 1937. Photo: Leigh Henningham

Specifically, they studied years that had at that point set a record as the hottest, along with record warm summers. They looked at global events and also those on a regional scale in five areas, including Australia and Europe.

The earliest extreme event the researchers found climate change had made significantly more likely was the then record breaking hot year across the planet in 1937, a time when the Spanish Civil War was still raging, the Hindenburg crashed and Joseph Lyon was Australian prime minister.

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The German airship Hindenburg crashes to the ground, tail first, in flaming ruins after exploding on May 6, 1937. Photo: Murray Becker

Before that year, Andrew King, from the University of Melbourne and one of the authors of the study, told Fairfax Media a clear climate change signal could not be detected above the natural variability in the weather system.

Since 1937 there have been 15 record hot years across the planet up to and including 2014, the last year the study captured (2015 was also a record hot year). All of those can also be attributed to some degree to climate change, the paper found, with those in recent decades found to be virtually impossible without human-caused global warming.

On a more local scale it took longer for the climate change signal to emerge. Dr King said regional weather was more a hostage to natural variability and other influences, meaning climate change had to become stronger to start registering a clear signal.

For Australia, the first record hot year the team found climate change had made significantly more likely was 1973. It was the same year (1972-73) that the first record hot Australia summer was also found to have human fingerprints on it.

There have been five record hot years, and two record hot summers, in Australia since where climate change's influence was found by the researchers.

Dr King said what was evident across all the different regions and types of heat events studied was how the influence of climate change became stronger as the decades went on.

For instance there was a three-fold increase in the chances of the 1980 being a record hot year in Australia. When 2013 set the same record, it was found to be 22-times more likely to have been because of human factors.

On a regional level the influence of climate change on extreme weather was found earliest in Australia. The researchers said the locally cooling influence of industrial aerosol likely caused a cooling period in Central England, Central US, Central Europe and East Asia during the 1970s, that delayed the emergence of a clear climate signal in those places.

Detecting the influence of climate change on individual weather events - know as attribution - is relatively new area of climate science.

Scientists test whether human-caused climate change is playing a role in making certain extreme weather events more likely by using complex computer simulations of the atmosphere.

They create two simulations, one that reflects the world as it is today with all the greenhouse gases that have been emitted since pre-industrial times, and one that excludes all that pollution.

The simulations are run thousands of times, and are then compared for how often different events emerge in the two scenarios.